ACCUMULATION OF WALL-ASSOCIATED PEROXIDASES DURING WOUND-INDUCED SUBERIZATION OF FLAX

Flax plants deposit ligno-suberin material around wounds. The depositi on of this material is first detected histochemically at 3 - 4 days af ter wounding. Preceding this, at 2 days after wounding, the levels of ionically bound and covalently bound but Driselase-solubilized wall pe roxidase activity are approximately four-fold higher than the control samples from unwounded tissue. Although this increase in wall-associat ed peroxidase activity is accompanied by an increase in the ability of the wall-associated enzymes to oxidize reduced nicotinamide adenine d inucleotides (NADH) to form hydrogen peroxide (H2O2), the ratio of NAD H oxidase to peroxidase activities is lower than the unwounded control samples. These figures suggest that wounding does not result in the a ccumulation of wall-associated peroxidases that have a particular affi nity for the generation of H2O2. It is intriguing, therefore, that cel l wall preparations from wounded tissue at 2 days have gained the abil ity to oxidize peroxidase substrates in the absence of added H2O2. Thi s suggests that these preparations can either generate their own H2O2 or contain covalently bound wall oxidases. An examInatIon of peroxidas e isozymes present in the wall-associated fractions suggests that the wound healing process is accompanied by increases in the abundance of specific cationic and anionic isozymes. Some of the cationic peroxidas es isozymes can also oxidise peroxidase substrates in the absence of H 2O2. The significance of the production of these oxidase/peroxidase is ozymes during wound healing is discussed.